Process for producing modified electronickel



Patented Dec. 30, 1952 UNITED STATES TENT OFFICE PROCESS FOR PRODUCINGMODIFIED ELECTRONICKEL of Delaware No Drawing.

Application October 12, 1948, Se-

rial No. 54,215. In Canada June 12, 1943 6 Claims.

The present invention relates to a process for the production in situ ofelectrodeposited nickel containing sulfur, and moreparticularly, to animproved process for the production in situ of electrodeposited 'nickelcontaining sulfur and suitable for use as anode in the electroplating ofprotective and/or decorative coatings of nickel.

The electroplating art has found that cast and rolled anodes of fusednickel are generally satisfactory from a technical aspect. However,fused nickel anodes require many manufacturing operations in preparingthe finished product and fused nickel anodes are comparativelyexpensive. The art has attempted to employ electrolytic nickel anodes inthe protective and/or decorative plating of nickel, but the use ofordinary electrolytic nickel anodes is attended with considerabledifliculty because of the poor activity of these anodes. As far as Iknow, no one at the present time is able to use ordinary electrolyticnickel anodes directly in place of fused nickel anodes without previousextensive revision of the electroplating operation. Furthermore, to myknowledge, prior art processes for producing electrolytic nickelmodified to permit its use directly as anode in commercial nickelplating operations have involved the incorporation in the electrolyteused in producing said electrolytic nickel of modifying agents whichrendered said electrolyte unsuitable for use in the production ofregular electro-refined nickel required to be devoid of said modifyingagents. Thus, prior art processes adapted to produce modifiedelectrolytic nickel anodes have suffered severe practical disadvantagesfrom the standpoint of the manufacture of high purity electrolyticnickel.

It has now been discovered that electronickel or cathode nickel anodessatisfactory for use directly as anodes in commercial nickel platingoperations can be produced in situ during the commercialelectro-refining of impure nickel.

It is an object of the present invention to provide a process forproducing electronickel or cathode nickel in situ which is satisfactoryfor use as anode in the electroplating of protective and/or decorativeelectroplates of nickel.

It is another object of the present invention to provide cathode nickelcontaining a critical amount of sulfur produced in situ without fusionfor use as anode in the electroplating of protective and/or decorativeelectroplates of nickel in baths having a pH more alkaline than pH 2(Q.).

It is a further object of the present invention to'provide a process forproducing electronickel or cathode nickel containing copper and sulfurand suitable for use as anode without fusion in electroplatingprotective and/or decorative electroplates of nickel.

The present invention also contemplates the production of electronickelor cathode nickel containing sulfur.

It is also within the contemplation of the present invention to providecathode nickel or electronickel containing copper and sulfur.

The present invention also provides for the production of electronickelor cathode nickel containing carbon, copper and sulfur.

Other objects and advantages will become apparent from the followingdescription.

Broadly stated, the present invention comprises the production ofelectrolytic nickel containing sulfur in critically controlled amountsbetween about 0.06% and about 0.5% substantially uniformly distributedtherethrough. The process embodying the invention comprises dissolvingimpure nickel anodically in a nickel electrolyte, purifying the impurenickel-containing electrolyte to remove substantially all iron, copper,arsenic and lead contained therein, introducing into the purifiedelectrolyte about 0.06 to about 0.5 grams per liter of sulfur dioxideand electrodepositing from said purified electrolyte substantially purenickel while depositing sulfur within the range of about 0.06% to about0.5% therein. A feature of the invention is that the electrolyteaddition agent, dissolved sulfur dioxide, may be readily removed fromthe electrolyte by aeration, etc., when desired, and the electrolyte maybe thereafter employed in the regular production of high purityelectrolytic nickel which is substantially devoid of sulfur. Thus, theprocess of the invention advantageously provides a method of producingsulfur-bearing electro nickel using regular production techniques.

Electrolytic nickel or cathode nickel containing amounts of sulfur asdescribed hereinbefore, particularly amounts of sulfur between about0.06% to about 0.2% obtained by using 0.06 to 0.2 grams per liter ofsulfur'dioxide in the electrolyte from which the electronickel isdeposited, is suitable for use directly (without fusion) as anode incommercial nickel plating baths. When employed as anode in commercialnickel plating baths such as the Watts-type bath, electrolytic nickelcontaining sulfur and produced according to the present inventionexhibits good corrosion characteristics and corrodes actively over awide range of pH up to about 5.5 (Q.) and over 3 a Wide range of currentdensity, e. g., about to about 100 amperes per square foot.

According to the present invention, electronickel or cathode nickelcontaining sulfur can be produced by introducing sulfur dioxide into theelectrolyte of a nickel electrorefining operation. That is to say,whether the electrolyte employed for the electrorefining of nickel bethe conventional all-sulfate electrolyte, which has been the one mostgenerally employed for this purpose, or the all-chloride electrolytewhich has not been used to so great an extent, or the novelsulfatechloride electrolyte disclosed in my U. S. Patent No. 2,394,874,granted February 12 1946, cathode nickel or electronickel containingsulfur can be roduced in substantially the same manner by addition ofcontrolled amounts of sulfur dioxide thereto. In other Words, whetherthe electrolyte employed be of the all-sulfate, the allchloride, or thesulfate-chloride type, it has been discovered that sulfur-containingnickel can be produced therefrom.

Suitable electrolytes which may be employed in carrying out theinvention to produce electrolytic nickel are aqueous electrolytescontaining or comprised essentially of. about 40 to about 80 grams perliter of nickel ions introduced into said electrolyte as at least onenickel compound selected from the group consisting of nickel chlorideand nickel sulfate, and about 15 to about grams per liter of boric acid.Addition agents selected from the group consisting of sodium sulfate andsodium chloride may be employed in amounts up 'to about 60 grams perliter, e. g., about 0.01 to about 60 grams per liter. Small amounts ofwetting agents, etc. may also be employed in the bath, e. g., about 0.10to about 0.25 gramjperliter. The electrolytes may be operated within thepH range of about 2.0 to about 4.5, andat temperatures within the rangeof about l00.to about 150? F. Nickel may be electrodepos'ited from theelectrolytes according to the invention at current densities of fromabout 10 to about- '20"amperes" per square foot. When the termall-sulfate electrolyte? is used herein I mean an aqueous electrolytecontaining or comprised essentially 'ofaboutlil to about 50 grams perliterfof nickel ions, about 85 to about 120 gramsjper literjof sulfateions, about 30 to about 50 grams per liter of sodium sulfate, about 15to aboutBO'grams per liter of boric acid and not more tlianabbutODZgrams per liter of chloride ion, e. g.; about 0.001 to about 002 gramper liter. This electrolyte is'operated for purposes of the invention ata pH of about 2.0 to about 4.5. When the term' all-chloride electrolyteis used herein I mean an aqueous electrolyte containing orcomprisedfes'sntially of about 40 to about 60 grams per liter' 'ofnickelions, about 78 to about 110- grams per liter of chloride ions, about 50to about 60 grams per liter of sodium chloride and sulfates present inamounts not greater than that usually considered as traces. For purposesof the invention, the all-chloride electrolyte may be operated at pHvalues within the range of about 2.0 toabout 4.5. When the termsulfatechloride electrolyte is used herein I mean an aqueous electrolytecontaining about 40 to about 60 grams per liter of nickel ions, about 65to about 105 grams per liter of sulfate ions, about 30 to about so gramsper liter of chloride ions, about 15 to about 30 grams per liter ofboric acid, and about 15 to about 25 grams per liter of sodium ionsintroduced into the bath in the form of at least one of the compoundsselected from the group sodium chloride and sodium sulfate. For purposesof the invention, the sulfate-chloride electrolyte may be operated at pHvalues within the range of about 2.0 to about 4.5.

As those skilled in the art know, the most generally-practiced methodfor electrorefining nickel involves the use of an all-sulfateelectrolyte. The process as generally employed is described in thearticle by P... L. Peek entitled Refining nickel-copper matte at PortColborne in the November 10, 1930, issue of Engineering and MiningJournal, published by the McGraW-Hill Book Company, Inc. The generalfeatures of the electrolytic cell preferably employed in the process aredescribed in the Hybinette U. 55. Patent No. 805,969.

Briefly stated, the process generally involves the anodic dissolution ina cell having a diaphragm separating the anode compartment from thecathode compartment of soluble impure cast nickel anodes generallyhaving anickel content of about to about 96%. For example, in oneindustrial operation, the impure nickel anodes contain about 94% toabout 96% nickel, about 2.5% to about 3.5 copper, about 0.7 to about0.9% cobalt, about 0.5% to about 1% iron, about 0.002% to about 0.004%lead, about 0.05% to about 0.7% arsenic, and about 0.5% to about 0.8%sulfur. In the electrolytic celldescribed in U. S. Patent No. 805,969,wherein a canvas diaphragm is provided between the cathode compartmentand the anode compartment, 3, hydrostatic pressure is maintained in thecathode compartment which substantially prevents migration of copper,cobalt, nickel, iron and similar cations from the impure anolyte throughthe diaphragm into the purified catholyte. The impure anodes aredissolved electrolytically in the anode compartment, and the resultingimpure anolyte is removed from the anode compartment, is purified, andthe purified electrolyte is then returnedto the cathode compartment ofthe cell. When the all-sulfate electrolyte is employed, the impureanolyte removed from the anode compartment is first subjected topurification to remove copper by cementation of the copper upon freshlyreduced nickel powder. After the copper has been removed by cementation,the iron, lead and arsenic are removed. The purified electrolyte is thenreturned to the cell as indicated hereinbefore. It is not ordinarilypracticable to continuously remove cobalt from all-sulfate nickelelectrolytes. When a sulfatechloride or all-chloride electrolyte isemployed in electrorefining nickel, some difierences in the purificationprocedure have been found advane tageous. Thus, for example, it has beenfound more satisfactory to remove lead, iron and arsenic from theelectrolyte before removing the copper.

In the sulfate-chloride electrolyte employed in the process disclosed inmy U. S; Patent No. 2,394,874., the ironin the. impure anolyte isprecipitated in the presence. of, cupric copper ions by oxidizing theiron with oxygen at a pH which permits the ion to hydrolyze to thehydroxide. Without separating the iron precipitates, arsenic and leadare oxidized with chlorine and then precipitated together with the iron.By suitable control of the pH of the solutionhcobalt can likewise beprecipitated with the iron, arsenic and lead. Thereafter, the copper isremoved in'any conventional manner, preferably by cementation' usingfreshly reduced nickel powder as the agent.

In the event that all of the cobalt has not been aeaasee removed byco-precipitation with iron, arsenic and lead, the residual cobalt isprecipitated by the. addition of chlorine and nickel carbonate toprovide an electrolyte substantially freefrom iron, lead, arsenic,copper and cobalt. Of course, the precious metals, gold, platinum andother metals of the platinum metal group together with sulfides ofcopper and nickel, present in the soluble impure anodes, remain on themore or less completely dissolved impure anodes as anode slimes inquantities dependent upon previous operations and the source of thenickel.

In carrying the invention into practice, it is preferred to add sulfurdioxide to the purified electrolyte before introduction of theelectrolyte into the cathode compartment of the plating operation insuch a manner as to ensure substantially uniform distribution of thesulfur dioxide throughout the electrolyte flowing to the cathode cell.Thus, for example, the sulfur dioxide may be introduced into theelectrolyte immediately after the last purification step or the purifiedelectrolyte may be introduced into a holding tank and the sulfur dioxidemay likewise be added to the electrolyte in the holding tank. On theother hand, the holding tank may be eliminated and sulfur dioxide may beintroduced into the stream of purified electrolyte a suitable distancebefore the purified electrolyte enters the cathode compartments.

It has been found that the sulfur content of cathode nickel orelectronickel produced in accordance with the principles of the presentinvention has a relation to the concentration of sulfur dioxide presentin the electrolyte in the cathode chamber. The following tabulationillustrates that the sulfur content of the resultant electronickel orcathode nickel expressed in percent is substantially equivalent to theconcentration of sulfur dioxide (expressed as grams per liter) presentin the electrolyte from which said electronickel or cathode nickel wasdeposited. The electrolyte pH originally was 5.0.

Electronickel or cathode nickel produced as described hereinbefore byintroducing sulfur dioxide into a nickel plating electrolyte underotherwise normal operating conditions of temperature and'ourrent densityis satisfactory for use directly, without heat treatment or fusion, asanodes when the sulfur content of the electronickel or cathode nickel ispreferably about 0.06 to 0.2%. When the electronickel is corroded in astandard hot Watts bath, the electronickel is active and exhibits goodcorrosion characteristics throughout the pH range of about 1.5 to 5.5(Q), i. e., p-H as measured by the standard quinhydrone electrode. Inaddition, the electronickel corrodes uniformly and does not produce anexcessive amount of sludge or loose nickel when corroded as anode in anickel plating bath.

It has been found that sulfur dioxide is unique for purposes of theinvention as compared to inorganic sulfur-containing compounds, such assalts, which might be considered to have analogous properties. Thus, ithas been found that additions of salts, like sulfites, etc., of thealkali and alkaline earth metals, to nickel electrolytes require furthermodifications of the electrolyte for the purpose of producingsulfur-containing: electronickel therefrom. Thus, it has been foundnecessary to make acid additions in order to control the pH ofelectrolytes containing such salts before the amounts of sulfurcontemplated by the invention can be introduced into the electronickeldeposited therefrom. However, unforeseen results have been achieved whenadditions of sulfur dioxide have been made to a nickel platingelectrolyte in accordance with the invention. The sulfur dioxide hasbeen found to perform a very important and unique dual function in thenickel plating bath, 1. e., additions of sulfur dioxide provide a sourceof sulfur for deposition in nickel electrodeposited from saidelectrolyte and, at the same time, provide the required pH control insaid electrolyte which enables deposition of sulfur along with thenickel electrodeposited from the nickel electrolyte to producesulfurcontaining electronickel. When the required pH control has beenestablished by introduction of sulfur dioxide into the electrolyte, itmust not be detrimentally affected as by the introduction of subsequentbasic additions and the resultant neutralization of the acid. If the pHcontrol is detrimentally affected, sulfur will not be deposited at thecathode along with the electrodeposited nickel as contemplated by theinvention when such an electrolyte is used in the production ofelectronickel.

Electronickel containing sulfur in excess of about 0.06% is somewhatbrittle and presents some difficulty in shearing although it issatisfactory for use directly, without fusion, as anode material in theprotective and/or decorative electroplating of nickel. This difficultymay be overcome by growing the cathodes to the desired size and thuseliminating the necessity of shearing. It has been discovered that thistendency to brittleness or the tolerance for sulfur of electronickel canbe overcome. When copper is added to electronickel and correlated to theamount of sulfur present therein, electronickel containing sulfur inexcess of about 0.06% can be produced which not only has all thedesirable anode corrosion characteristics, but in addition has improvedductility. At least about 0.05% copper should be introduced into thesulfurcontaining electronickel of the invention to promote ductilitytherein. In the presence of such amounts of copper up to about 0.15%,the sulfur content of cathode nickel can be from about 0.06% to as muchas 0.15% to provide electronickel which is satisfactory for use as anodewithout heat treatment and in the unfused condition throughout the pHrange of about 1.5

to about 5.5 (Q), and to provide copper-sulfurbearing electronickelwhich has less tendency to brittleness and can be sheared into sizessuitable for use as anode.

The copper-bearing modified electronickel containing sulfur may beproduced in a manner quite analogous to that described hereinbefore forthe production of modified electronickel containing sulfur. That is tosay, an electrolyte soluble copper salt, such as copper sulfate orcopper chloride or a copper compound which when introduced into thepurified electrolyte is converted to a soluble form, is added to theelectrolyte in carefully controlled amounts sufficient to provide anamount of copper within the range of about 0.01 to about 0.03 gram perliter of electrolyte. The copper compound may be introducedsimultaneously with thesulfur dioxide, or atany other suitable time orplace which will permit substantially complete mixing of the coppercompound with the purified electrolyte before the electrolyte enters thecathode compartment. In other words, a solution of copper sulfate, forexample, may be introduced into the electrolyte after the finalpurification thereof wherein the electrolyte has been freed from suchimpurities as iron, lead, arsenic and copper, or the-copper salt or thecopper compound may be introduced into a holding tank together withsulfur dioxide as indicated hereinbefore. Alternatively "(although lesspreferably, because of control difiiculties), the removal of copper fromthe impure electrolyte may be regulated to leave in 'thepurifiedelectrolyte a residual amount of copper within the limits set forthhereinbefore. In other respects the production of copper-bearingmodified electronickel containing sulfur is carried out under the sameconditions as those employed to produce substantially copper-freemodified electronickel containing sulfur.

It has been found that the tolerance of electronickel for sulfur can beincreased by introducing into the electronickel a controlled amount ofcarbon with or without the controlled amount of copper and thatdesirable anode properties including appearance, etc. are improved bysuch carbon additions as well as the aforedescribed copper additions.That is to say, electronickel containing about 0.02% to 0.04% carbon,about 0.05% to 0.15% copper, and about 0.10% to 0.15%

sulfur can be produced in an all-sulfate electrolyte or an all-chlorideelectrolyte or a mixed sulfate-chloride electrolyte by introducing intothe electrolyte acetylene as well as a copper salt and sulfur dioxide.The acetylene is introduced into the electrolyte in amounts sufficientto provide a concentration of about 0.001 to about 0.005 grams ofacetylene per liter of electrolyte. Simultaneously, provision is made toprovide about 0.01 to about 0.03 gram per liter of copper andabout 0.10to about 0.15 gram of sulfur dioxide per liter of electrolyte. Thetemperature, current density and pH of the electrolyte duringelectrodeposition of the carbon-copper-bearing modified electronickelcontaining sulfur are substantially the same as those setforthhereinbefore for the manufacture of the novel sulfurbearingelectronickel of the invention.

When desired, electronickel containing sulfur and carbon butsubstantially devoid of copper can be produced by making suitableadditions within the ranges set forth hereinbefore of sulfur dioxide andacetylene to the purified electrolyte and maintaining suitableconcentrations of sulfur .dioxide and acetylene in the purifiedelectrolyte entering the cathode compartment. Thus, when a sulfurdioxide concentration of about0.06 to about 0.2 gram per liter and anacetylene con centration of about 0.001 to about 0.005 gram per "literis maintained in the purified catholyte, electrolytic nickel containingabout 0.06% to bearingielectrolytic nickelor cathode ,nlckel containingabout 0.06% to about'0.2% sulfur. Sulfur-carbon-bearing electrolyticnickel or cathode nickel containing about 0.1% to about 0.15% .sulfurand about 0.01% to about 0.04% carbon also gives very satisfactoryresults when used as anode in the decorative and/or protectiveelectroplating of objects with nickel. Similarly,sulfur-carboncopper-bearing electrolytic nickel or cathode nickelcontaining about 0.1% to about 0.15%sulfur, about 0.01% toabout 0.04%carbon and about 0.05% to about 0.15%copper also gives very satisfactoryresults. When 'sulfur-copper-bearing electrolytic nickel isdesired,sulfur contents between about 0.1% and about 0.15% together with coppercontents between about 0.05% and about 0.15% have been found to bepreferable.

As those skilled in the art -know, electrolytic nickel is of very highpurity and varies but slightly in composition whether produced in anall-sulfate electrolyte, an all-chloride electrolyte, or a mixedsulfate-chloride electrolyte. Electrolytic nickel produced according tothe present invention may contain, in addition to the amounts of sulfurand/or copper and/or carbon disclosed hereinbefore, about 0.001% toabout 0.005% iron and about 0.01% to 0.8% cobalt.

This application is a continuation-in-part of my co-pending U. S.application Serial No. 197,601, filed August 6, 1943, now Patent No.2,453,757.

Although the present invention has'been described in conjunction withcertain preferred embodiments thereof, those skilled in the art willunderstand that variations and modifications thereof can be made. Suchvariations and modifications are to be considered within the purview andscope of the specification and the appended claims.

I claim:

1. The process of electrorefining impure metallic nickel to producesubstantially pure nickel containing copper, carbon and sulfur andhaving good activity when employed as anode in electroplating nickelfrom nickel electroplating baths having a pH up to 5.5 (Q.) whichcomprises anodically corroding an impure nickel anode to produce animpure electrolyte containing the impurities copper, arsenic, iron andlead, purifying said electrolyte to produce a purified electrolytesubstantially devoid of copper, arsenic, iron and lead, introducing intosaid purified electrolyte a sufficient amount of sulfur dioxide toprovide a concentration of about 0.1 to 0.15gram1per liter of sulfurdioxide, a sufficient amount of; anelectrolyte-soluble copper salt toprovide a concentration of about 0.01 to 0.03 gram per liter of copper,and a sufficient amount of .acetylene to provide a concentration ofabout 0.001 to 0.005 gram per liter therein, and electrodepositingsubstantially pure nickel from said electrolyte in the: presence of saidamounts OfESlllflll' dioxide, copper and acetylene without neutralizingthe effects of said sulfur dioxide upon the electrolyte ,pH whiledepositing sulfur within the range of about 0.1% to 0.15%, copper withinthe range of about 0.05 to 0.15% and carbon .within the range of about0.01% to 0.04% in said nickel.

2. The process of electrorefining impure metallic nickel to producesubstantially pure nickel containing carbon and sulfur :and having goodactivity when employed as anode in electroplating nickel from nickelelectroplating baths having a pH up to 5.5 '(Q.) which. comprisesanodically corroding. an. impure nickelv arfodeto. produce an impureelectrolyte containing the impurities copper, arsenic, iron and lead,purifying said electrolyte to produce a purified electrolytesubstantially devoid of copper, arsenic, iron and lead, introducing intosaid purified electrolyte a suificient amount of sulfur dioxide toprovide a concentration of about 0.1 to 0.15 gram per liter of sulfurdioxide and a sufficient amount of acetylene to provide a concentrationof about 0.001 to 0.005 gram per liter therein, and electrodepositingsubstantially pure nickel from said electrolyte in the presence of saidamounts of sulfur diox de and acetylene without neutralizing the effectsof said sulfur dioxide upon the electrolyte pH while depositing sulfurwithin the range of about 0.1% to 0.15% and carbon within the range ofabout 0.01% to 0.04% in said nickel.

3. The process of electrorefining impure metallic nickel to producesubstantially pure nickel containing copper and sulfur and having goodactivity when employed as anode in electroplating nickel from nickelelectroplating baths having a, pH up to 5.5 (Q.) which comprisesanodically corroding an impure nickel anode to produce an impureelectrolyte containing the impurities copper, arsenic, iron and lead,purifying said electrolyte to produce a purified electrolytesubstantially devoid of copper, arsenic, iron and lead, introducing intosaid purified electrolyte a sufficient amount of sulfur dioxide toprovide a concentration of about 0.1 to 0.15 gram per liter of sulfurdioxide and a sufficient amount of an electrolyte-soluble copper salt toprovide a concentration of about 0.01 to 0.03 gram per liter of copper,and electrodepositing substantially pure nickel from said electrolyte inthe presence of said amounts of sulfur dioxide and copper withoutneutralizing the effects of said sulfur dioxide upon the electrolyte pHwhile depositing sulfur within the range of about 0.1% to 0.15% andcopper within the range of about 0.05% to 0.15% in said nickel.

4. The process of electrorefining impure metallic nickel to producesubstantially pure nickel containing copper and sulfur and having goodactivity when employed as anode in electroplating nickel from nickelelectroplating baths having a PH up to 5.5 (Q.) which comprisesanodically corroding an impure nickel anode to produce an impureelectrolyte containing the impurities copper, arsenic, iron and lead,purifying said electrolyte to produce a purified electrolytesubstantially devoid of copper, arsenic, iron and lead, introducing intosaid purified electrolyte a sufficient amount of sulfur dioxide toprovide a concentration of about 0.06 to 0.15 gram per liter of sulfurdioxide and a sufficient amount of an electrolyte-soluble copper salt toprovide a concentration of about 0.01 to 0.03 gram per liter of copper,and electrodepositing substantially pure nickel from said electrolyte inthe presence of said amounts of sulfur dioxide and copper withoutneutralizing the effects of said sulfur dioxide upon the electrolyte pHwhile depositing sulfur within the range of about 0.06% to 0.15% andcopper within the range of about 0.05% to 0.15% in said nickel.

5. The process for producing electrolytic nickel satisfactory for usedirectly in nickel electroplating baths as a nickel plating anode andhaving good activity up to about pH 5.5- (Q.) which comprisesincorporating sulfur dioxide into a purified nickel refining electrolyteselected from the group consisting of all-sulfate electrolytes,allchloride electrolytes, and sulfate-chloride electrolytes to provide aconcentration of about 0.06 to about 0.2 gram per liter of sulfurdioxide in said electrolyte and to substantially reduce the pH of saidelectrolyte, the electrolyte pH after said sulfur dioxide introductionbeing within the range of about 2.0 to about 4.5, and said sulfurdioxide being the sole active agent for introducing sulfur into nickelelectrodeposited from said 10 eletcrolyte, electrodepositingsubstantially pure nickel from said electrolyte in the presence of saidsulfur dioxide without neutralizing the effects of said sulfur dioxidein reducing the electrolyte pH while depositing sulfur within the rangeof about 0.06% to about 0.2% in said nickel to produce electrolyticnickel having good activity when used directly as anode inelectrodepositing nickel from nickel electroplating baths, thereafteraerating said electrolyte to provide a purified nickel refiningelectrolyte substantially devoid of sulfur dioxide and satisfactory foruse in electrodepositing electrolytic nickel of high puritysubstantially devoid of sulfur.

6. The process for producing electrolytic nickel satisfactory for usedirectly in nickel electroplating baths as a nickel plating anode andhaving good activity up to about pH 5.5 (62.) which comprisesincorporating sulfur dioxide into a purified nickel refining electrolyteselected from the group consisting of all-sulfate electrolytes,all-chloride electrolytes, and sulfate-chloride electrolytes to providea concentration of about 0.06 to about 0.5 gram per liter of sulfurdioxide in said electrolyte and to substantially reduce the pH of saidelectrolyte, the electrolyte pH after said sulfur dioxide introductionbeing within the range of about 2.0 to about 4.5, and said sulfurdioxide being the sole active agent for introducing sulfur into nickelelectrodeposited from said electrolyte, electrodepositing substantiallypure nickel from said electrolyte in the presence of said sulfur dioxidewithout neutralizing the efiects of said sulfur dioxide in reducing theelectrolyte pH while depositing sulfur within the range of about 0.06%to about 0.5% in said nickel to produce electrolytic nickel having goodactivity when used directly as anode in electrodepositing nickel fromnickel electroplating baths, and thereafter aerating said electrolyte toprovide a purified electrolyte substantially devoid of sulfur dioxideand satisfactory for use in electrodepositing nickel of high puritysubstantially devoid of sulfur.

LOUIS SECONDO RENZONI.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Electrochemical Society, published 1942, pages242, 243.

Roscoe et al., Treatiseon Chemistry, vol. I, 1920, pp. 399, 401, 406,407.

1. THE PROCESS OF ELECTROREFINING IMPURE METALLIC NICKEL TO PRODUCESUBSTANTIALLY PURE NICKEL CONTAINING COPPER, CARBON AND SULFUR ANDHAVING GOOD ACTIVITY WHEN EMPLOYED AS ANODE IN ELECTROPLATING NICKELFROM NICKEL ELECTROPLATING BATHS HAVING A PH UP TO 5.5 (Q.) WHICHCOMPRISES ANODICALLY CORRODING AN IMPURE NICKEL ANODE TO PRODUCE ANIMPURE ELECTROLYTE CONTAINING THE IMPURITIES COPPER, ARSENIC, IRON ANDLEAD, PURIFYING SAID ELECTROLYTE TO PRODUCE A PURIFIED ELECTROLYTESUBSTANTIALLY DEVOID OF COPPER, ARSENIC, IRON AND LEAD, INTRODUCING INTOSAID PURIFIED ELECTROLYTE A SUFFICIENT AMOUNT OF SULFUR DIOXIDE TOPROVIDE A CONCENTRATION OF ABOUT 0.1 TO 0.15 GRAM PER LITER OF SULFURDIOXIDE, A SUFFICIENT AMOUNT OF AN ELECTROLYTE-SOLUBLE COPPER SALT TOPROVIDE A CONCENTRATION OF ABOUT 0.01 TO 0.03 GRAM PER LITER OF COPPER,AND A SUFFICIENT AMOUNT OF ACETYLENE TO PROVIDE A CONCENTRATION OF ABOUT0.001 TO 0.005 GRAM PER LITER THEREIN, AND ELECTRODEPOSITINGSUBSTANTIALLY PURE NICKEL FROM SAID ELECROLYTE IN THE PRESENCE OF SAIDAMOUNTS OF SULFUR DIOXIDE, COPPER AND ACETYLENE WITHOUT NEUTRALIZING THEEFFECTS OF SAID SULFUR DIOXIDE UPON THE ELECTROLYTE PH WHILE DEPOSITINGSULFUR WITHIN THE RANGE OF ABOUT 0.1% TO 0.15%, COPPER WITHIN THE RANGEOF ABOUT 0.05% TO 0.15% AND CARBON WITHIN THE RANGE OF ABOUT 0.01% TO0.04% IN SAID NICKEL.